Many electronic devices, such as mobile telephones, pagers, PDAs, etc., are provided with a vibrator that silently alerts a user when a message or an incoming call is received. The vibrator usually comprises a small electromotor provided with an unbalanced mass at a rotating shaft, and it is usually mounted in the electronic device by means of an elastic fitting, such as a rubber grommet or a flexible metal holder.
In electronic devices provided with fixed covers, such as a front cover and a back cover, the vibrator is conventionally mounted in a recess provided at the inner surface of one of the covers. However, in the electronic devices to which the invention relates, i.e. electronic devices provided with at least one exchangeable cover, the vibrator is positioned away from the exchangeable cover in order to ensure that the user does not accidentally destroy the vibrator or loosen it from its contact with the PCB. In these electronic devices the vibrator may be mounted in a recess of a not-exchangeable cover or in a holder that is connected to the PCB. Electronic devices with a vibrator mounted in this manner is known from e.g. US-A1-2002/0027009 and US-B1-6,177,881.
However, in cases where the vibrator is located away from the exchangeable cover the vibration that is produced when the unbalanced mass rotates must travel through a number of elements, such as the PCB and internal frame parts, before it reaches the exchangeable cover. The passage through these various elements dampens the vibration before it reaches the exchangeable cover, whereby the vibration that is experienced at the exchangeable cover is substantially weaker than the vibration at the location of the vibrator.
Electronic devices such as mobile telephones and components are therefore to an increasing extent made smaller and smaller. However, if the vibration waves must travel through a number of elements before they reach the cover, a relatively large vibrator must be employed in order to ensure that the experienced vibration has a certain magnitude. A smaller vibrator can be employed if it is mounted directly in a recess provided in the exchangeable cover, which, however, is undesirable since it would entail that the vibrator must be dismounted from the cover and re-mounted in the new cover. If such operation is necessary there is a great risk that the vibrator is lost or re-mounted wrongly which may cause the vibrator or other electronic components to be destroyed when the new cover is mounted.
It is therefore an object of the invention to provide an electronic device as mentioned in the opening paragraph in which it is possible to use a small vibrator that cannot be accidentally destroyed or loosened from the PCB and that is in relatively close contact with the exchangeable cover.